1. Field of the Invention
The present invention relates to systems and methods for installing expansion joints in cementitious materials.
2. Relevant Art
Concrete is a major component of construction projects. One well-known property of concrete is that temperature changes can cause it to contract and expand. Over time, such repeated contractions and expansions can crack and fracture the concrete. For this reason, expansion joints are installed within newly-poured concrete to keep it from cracking and fracturing.
Expansion joints provide a space into which separated segments of adjacent concrete slabs can expand without cracking. Expansion joints are also used when joining a newly-poured concrete slab to an existing structure to prevent damage to the structure, to the slab, or to both. One form of expansion joint is merely a space between two segments of a slab. A disadvantage with this form of expansion joint, however, is that the joint becomes a repository for rain, snow, ice, dirt, and other harmful elements.
Another form of the expansion joint is created by inserting one of a number of various types of compressible expansion joint material between segments of the slab. After the joint material has been installed within the fresh concrete, the concrete around the expansion joint is smoothed level with the top edge of the expansion joint so that the top edge of the expansion joint is exposed and visible in the finished concrete. Many types of compressible expansion joint material can be used to create an expansion joint. Examples of such expansion joint material include constructions created of fiber, sponge rubber, plastic, or cork. Note that often practitioners of the art will refer to the expansion joint material used to create an expansion joint as the expansion joint itself. For example, an uninstalled length of expansion joint material might be called an expansion joint.
One prior art technique for installing expansion joints is described in U.S. Pat. No. 4,198,176 (“the '176 patent”). The '176 patent discloses an apparatus with a trough for holding expansion joint material described as decorative joint material. The apparatus and expansion joint material it holds are positioned within the area of a pour. Concrete is then poured over the apparatus and the joint material. The apparatus holding the joint material remains embedded within the concrete. A disadvantage to this method is that the apparatus is not reusable. This leads to increased expense in installing expansion joints.
Another method for installing expansion joints in freshly-poured concrete employs grade stakes to keep a length of joint material in position and to keep it from bowing. Grade stakes are driven into the ground on one side of a length of joint material to give the joint material support. A form board is sometimes placed between the grade stakes and the joint material to provide additional support. Any existing structures, landscaping, finished concrete, or the like appearing near where an expansion joint is to be installed are usually covered with some protective material, like plastic sheeting, to protect from concrete splatter.
Concrete is then poured on either side of a staked length of joint material. For lengths of joint material set against existing structures, however, concrete is poured on only one side of the joint material since the structure abuts the opposite side. Installers then scoop some of the concrete away from the grade stakes and hammer the stakes completely into the ground until no part of a grade stake appears above ground. If a form board was used to help support the joint material, the form board is removed at this time. Note that it is also possible to pull the grade stakes out of the ground rather than hammering them in. Many installers, however, find it easier simply to hammer the grade stakes into the ground. Hammering through fresh concrete causes concrete splatter. The protective material, such as plastic sheeting, protects nearby structures, landscaping, finished concrete, and the like from the splatter. The concrete around the newly-installed expansion joint is then smoothed to approximately the height of the top edge of the joint material. This same process is done for each length of joint material in the pour area. A disadvantage of this method of installing expansion joints is the added effort and materials required.
What is needed is a system and method for installing expansion joints in freshly-poured concrete that keeps a length of expansion joint material from slipping out of position during installation, that prevents the length of joint material from deforming or breaking during installation, and that reduces the need for non-reusable materials.